Reduce package distribution size

[kbwestfall]

The primary goal of this PR is to reduce the size of the package distribution installed using pip. To do so, I

1. refactored @tbowers7 cache system, largely to make the code more general,
2. added more data files to the list being controlled by the cache
3. removed the doc/ directory from the distribution

For item 1, I added the pypeitdata.py and cache.py files, which are refactored pieces of what was data/utils.py, and then I moved some of the load_* functions from data/utils.py into io.py. With this refactor, I've removed the pypeit.data module and replaced it with the pypeit.dataPaths instance; see the changes to the main __init__.py file. If this is accepted, I'd like to make the data/ directory exclusively for data files; i.e., it should not have any code in it.

After some testing, this reduces the size of the tar file from ~145MB for version 1.15.0 to about 12MB. The big ticket items were the test data files, some of the standards, and doc figures directory.

There's no hurry on this one, but I wanted to issue this so that everyone can start to comment.

[kbwestfall]

Test "pass". All of the failures are in NIRSPEC, presumably because of recent changes to the raw data available. I'll re-run after the NIRSPEC branch is merged.

Test Summary
--------------------------------------------------------
--- PYTEST PYPEIT UNIT TESTS PASSED  257 passed, 56 warnings in 399.69s (0:06:39) ---
--- PYTEST UNIT TESTS FAILED  3 failed, 130 passed, 171 warnings in 937.68s (0:15:37) ---
--- PYTEST VET TESTS PASSED  61 passed, 73 warnings in 5528.28s (1:32:08) ---
--- PYPEIT DEVELOPMENT SUITE FAILED 1/237 TESTS  ---
Failed tests:
    keck_nirspec/LOW_NIRSPEC-1 pypeit
Skipped tests:
Testing Started at 2024-03-07T21:33:16.697132
Testing Completed at 2024-03-08T10:08:43.978332
Total Time: 12:35:27.281200

[rcooke-ast]

This is impressive @kbwestfall - job very well done! I only have a few minor points, but the new approach is a lot better than before. I also have one general question... If a user updates their version of PypeIt, will this require them to re-download all data files when needed (or, only if those data files have been updated)? It just wasn't clear to me how any updated (i.e. changed from one release to the next release) data files are being managed. Thanks again!

I have no major issues with this PR, so I'm approving.

[tbowers7]

Looks great. Thanks for addressing the Windows path questions.

[kbwestfall]

There is a test failure, but it's because of a recent change to the files in the relevant Keck/HIRES dataset. The vet-test failure is related. So I think this one is ready to go.

Test Summary
--------------------------------------------------------
--- PYTEST PYPEIT UNIT TESTS PASSED  256 passed, 56 warnings in 431.72s (0:07:11) ---
--- PYTEST UNIT TESTS PASSED  148 passed, 167 warnings in 1038.48s (0:17:18) ---
--- PYTEST VET TESTS FAILED  1 failed, 60 passed, 96 warnings in 5677.00s (1:34:37) ---
--- PYPEIT DEVELOPMENT SUITE FAILED 1/239 TESTS  ---
Failed tests:
    keck_hires/J1723+2243_W241_RED_C5_ECH_-0.15_XD_0.90_2x2 pypeit
Skipped tests:
Testing Started at 2024-06-12T01:28:58.711750
Testing Completed at 2024-06-12T14:16:18.163584
Total Time: 12:47:19.451834